Imported evaporative light scattering detectorIt is a universal detection device based on the principle of light scattering, widely used in separation and analysis fields such as high performance liquid chromatography (HPLC), ultra-high performance liquid chromatography (UHPLC), and capillary electrophoresis (CE). Its core advantage lies in breaking away from the dependence of traditional detection techniques on the optical properties of samples, and being able to detect substances without UV absorption, fluorescence, or electroactivity, such as sugars, lipids, surfactants, amino acids, drugs, and polymers.
Working principle: The detection process of ELSD consists of three key steps: atomization, evaporation, and light scattering detection. The liquid sample flowing out of the chromatographic column enters the atomizer and mixes with high-speed inert gas (such as nitrogen) to form tiny droplets, forming aerosols. Aerosols enter the heated drift tube, and the solvent in the droplets rapidly evaporates, leaving only sample particles. These particles generate light scattering when passing through a beam of light (such as a laser or LED light source), and the intensity of the scattered light is proportional to the concentration of the sample. The photoelectric sensor collects scattered light and converts it into an electrical signal, ultimately outputting a chromatogram.
Imported evaporative light scattering detectorOperation steps:
1. Check before startup
Preparation of mobile phase: Accurately prepare the required mobile phase according to experimental requirements, ensuring its purity and composition meet analytical requirements.
Connecting pipeline: Securely connect the outlet pipeline of the chromatography column to the inlet of the detector to prevent loosening or leakage during operation.
Check the gas source: Turn on the air or nitrogen source, and the input pressure is usually set to 350kPa (the specific pressure may vary depending on the instrument model and manufacturer's requirements, please refer to the instrument manual), to ensure that the gas is pure and free of particles and impurities, so as not to affect the detection results and damage the instrument components.
2. Startup and initialization
Turn on the instrument power: Turn on the power switch on the back panel of the detector, and the instrument starts self checking. The operation window displays that the instrument is in "standby mode" and shows the timer time. At the same time, it automatically displays the last method setting used before the last shutdown.
Exhaust and transport mobile phase: Exhaust the required mobile phase, remove bubbles in the pipeline, and then start the pump to transport the mobile phase. Ensure that the siphon tube in front of the instrument is filled with liquid and the droplets in the atomization tube are normal.
Rinse the equilibrium mobile phase: Set the appropriate Gain value (used to amplify the signal, adjusted according to the actual peak shape, too large may cause flat top f), drift tube temperature (selected according to the properties of the mobile phase and the measured substance, usually using low boiling point solvents as the mobile phase, the maximum set value of drift tube temperature is generally 80 ℃, and can be set to a maximum of 100 ℃ during maintenance and cleaning), turn on the LED light, and start rinsing the equilibrium mobile phase.
Zero adjustment and baseline stability: After flushing is completed, ensure that the baseline pressure is stable, perform zero adjustment operation to reset the instrument output signal to zero, and provide accurate reference for subsequent sample detection.
3. Parameter settings
According to the sample and analysis requirements: Set key parameters such as atomization gas flow rate, mobile phase flow rate, drift tube temperature, and impactor position through the operation panel or software interface. For example, the flow rate of atomizing gas determines the size of the droplets formed during atomization. The higher the gas flow rate, the smaller the droplets formed, but small particles scatter less light and have smaller signals. Therefore, it is necessary to determine the gas flow rate that produces the optimal signal-to-noise ratio through experiments; The selection of the impactor position depends on the composition of the mobile phase, flow rate, and volatility of the analyte, with the key being to strike an appropriate balance between sensitivity and sufficient volatility of the mobile phase.
4. Sample analysis
Injection test: The processed sample is injected into the chromatography system through an automatic injector or manual injection method. The sample is transported to the chromatography column for separation, and the separated components are sequentially introduced into the evaporative light scattering detector.
Data recording and analysis: The detector detects the components of the sample, generates corresponding signal intensity changes, and these data are recorded. By using supporting software to process and analyze data, such as integration and calibration, quantitative and qualitative information of the sample can be obtained.
5. Shutdown and Cleaning
Rinse the pipeline and atomizer: After the test is completed, rinse the pipeline and atomizer with a suitable solvent for more than 30 minutes to remove residual samples and impurities, prevent blockage and corrosion.
Stop pumping liquid: After flushing is complete, stop pumping liquid and wait for a period of time (recommended at least 30 minutes) to allow the liquid in the pipeline to be fully discharged.
Turn off the gas source and power: First turn off the gas source, then turn off the main power of the detector. At the same time, check the waste liquid bottle and condenser bottle, promptly pour out excess liquid, and prevent liquid overflow from polluting the environment or damaging the instrument.